diaper rash

So
My almost 3 week baby seems to have a diaper rash (hus bum is red) and he is crankier than usual. We let him have some air time last time he was changed and we've been using a warm wash cloth to wipe his toosh.. Also I will start using zinc creams which should help. I try and change him as soon as I see he needs to be changed. Any advice for a FTM? Thanks